Cold Start V8 Roughness!

[hairdryer33]

First start of the day runs crap until idled for five mins. Try to drive then it gets rougher and stalls, try to restart but winds over constantly (10seconds on starter sometimes) then when it does start I cant touch the throttle or it will stall again untill the idle smooths out. I have no other idle issues other than this. Rb25

Edited November 17, 2014 by hairdryer33

[Dose Pipe Sutututu]

Didn't you tell us a few threads ago your fuel pump is cactus?

[hairdryer33]

Yep, problem still remains

[Dose Pipe Sutututu]

so replace the fuel pump

[hairdryer33]

I did, brand new pump. Problem is still there. What else could be causing this? It has a low cold start idle like its missing one or two cylinders then warms up and comes right. If it stalls when running rough its a bitch to start, almost like an old carby which is flooded

[Josh080691]

Check coilpacks / spark plugs / afm and cas and all wiring related. Then report back

[Dose Pipe Sutututu]

do you have access to a consult cable or an ECUtalk? (http://www.ecutalk.com/consultlcd.aspx)

I have a feeling either your water temp sensor (two wire one) is cactus

[blind_elk]

Cold start valve (the "torpedo" one) could be cactus. AAC valve may not be set correctly.

Could need a good clean of the injectors.

What is the condition of the spark plugs?

Will it start if you give it a bit of throttle?

[hairdryer33]

Ls1 coils made no difference compared to stock. New plugs gapped to .8 2nd afm cleaned with proper electrical cleaner, two different cas, no difference. Dont need a consult cable, did the old check engine diagnostic check engine light for fault cods, none shown. Once stalled I have to hold throttle flat after about 10seconds of cranking it fires, but really rough. Tps has been reset and tested countless times.

[hairdryer33]

Ive ran a few tanks a injector cleaner but no difference. Guess it cant hurt to rip them out to be cleaned

[RamR33]

Could be either ECU or injectors.

Most likely injectors.

[hairdryer33]

Its my second ecu still doew the same. Number 6 injector has the little plastic bit at the end missing but cant see how that would effect it

[Ben C34]

There's not much that makes the car run.

There's not much that makes the car run bad.

Stop swapping ecu's as they are the least likely thing to fail. Cas, afm, injectors, and of course cold start valve, aac.

[Dose Pipe Sutututu]

and maybe adjust your IACV correctly and disconnect your stock O2 if it's cactus

[hairdryer33]

Exactly

[blind_elk]

Once stalled I have to hold throttle flat after about 10seconds of cranking it fires, but really rough.

That suggests that the engine is flooding, probably due to dirty injector needles not closing properly and letting fuel into the cylinders when its not needed.

So, time to rip out the injectors and have them sonic cleaned.

[hairdryer33]

Will know for sure very soon. Thanks all for the help

[Dose Pipe Sutututu]

Might as well upgrade the injectors whilst your at it.

You'll have to do it sooner or later lol

So save up for an aftermarket ECU or Nistune starting tomorrow.

[hairdryer33]

Will do, already got the ignition side of things sorted, ls1 coils so now its a matter of saving

[hairdryer33]

Replaced fuel pump, made a big difference and drive 100% better but still the cold start issue remains. The part im looking for iac valve, is that one the same unit as the idle screw adjuster? If so, what does that other part do where its got the rubber ,pipe from the intake connecting to it?